:root {
  --bg: #f4ecde;
  --paper: #fbf7ef;
  --ink: #261814;
  --muted: #64524d;
  --line: rgba(38, 24, 20, 0.12);
  --accent: #8a5a36;
  --accent-soft: #d3b28e;
  --shadow: 0 18px 44px rgba(64, 38, 24, 0.12);
  --display: "Iowan Old Style", "Songti SC", serif;
  --sans: "Avenir Next", "PingFang SC", sans-serif;
  --content: 1180px;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  color: var(--ink);
  font-family: var(--sans);
  background:
    radial-gradient(circle at top left, rgba(138, 90, 54, 0.18), transparent 24%),
    radial-gradient(circle at top right, rgba(55, 32, 25, 0.14), transparent 18%),
    linear-gradient(180deg, #f8f1e4, #f1e7d6);
}
a { color: inherit; text-decoration: none; }
img { max-width: 100%; display: block; }
.site-shell { position: sticky; top: 0; z-index: 40; backdrop-filter: blur(16px); background: rgba(248, 241, 228, 0.76); border-bottom: 1px solid var(--line); }
.shell-bar { max-width: var(--content); margin: 0 auto; padding: 16px 24px; display: flex; justify-content: space-between; align-items: center; gap: 16px; }
.brand-mark { font-family: var(--display); font-size: 1.18rem; }
.shell-nav { display: flex; gap: 16px; color: var(--muted); }
.page-wrap { max-width: var(--content); margin: 0 auto; padding: 28px 24px 72px; }
.hero, .section-block, .info-block { background: rgba(251, 247, 239, 0.86); border: 1px solid var(--line); box-shadow: var(--shadow); }
.hero { display: grid; grid-template-columns: minmax(0, 1.2fr) minmax(280px, 0.8fr); gap: 28px; align-items: center; padding: 28px; border-radius: 32px; }
.hero-copy h1, .section-head h1, .section-head h2, .info-block h2, .info-block h3, .card-copy h3 { font-family: var(--display); margin: 0; }
.hero-copy h1 { font-size: clamp(2.4rem, 4vw, 4.6rem); line-height: 1.08; }
.hero-summary, .section-head p, .card-copy p, .info-block p, .info-block li, .path-card span, .route-item span { color: var(--muted); line-height: 1.78; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 20px; }
.action-pill { padding: 12px 18px; border-radius: 999px; background: var(--ink); color: #f8f2e7; }
.action-pill.subtle { background: rgba(38, 24, 20, 0.08); color: var(--ink); }
.paper-frame, .hero-cover { background: linear-gradient(180deg, #fffdf9, #efe3d0); border-radius: 24px; padding: 14px; border: 1px solid rgba(38, 24, 20, 0.14); }
.card-thumb { aspect-ratio: 4 / 3; margin: 12px; padding: 12px; }
.card-thumb img, .hero-cover img, .viewer-thumb img { width: 100%; height: 100%; object-fit: contain; background: #fffdfa; border-radius: 14px; }
.section-block { margin-top: 28px; padding: 26px; border-radius: 28px; }
.section-head { display: flex; flex-direction: column; gap: 10px; margin-bottom: 20px; }
.eyebrow { margin: 0 0 8px; font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.12em; color: var(--accent); }
.part-grid, .card-grid, .route-grid, .deep-grid { display: grid; gap: 18px; }
.part-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.card-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.chapter-grid, .case-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.concept-grid, .plate-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.chapter-card, .case-card, .principle-card, .plate-card, .part-card, .path-card, .route-item, .source-item-deep { background: rgba(255, 252, 246, 0.96); border: 1px solid var(--line); border-radius: 22px; }
.chapter-card, .case-card, .principle-card, .plate-card { overflow: hidden; display: flex; flex-direction: column; min-height: 100%; }
.card-copy { padding: 0 18px 18px; display: flex; flex-direction: column; gap: 10px; }
.card-copy h3 { font-size: 1.22rem; line-height: 1.26; }
.tag-row { display: flex; flex-wrap: wrap; gap: 8px; }
.mini-tag { font-size: 0.78rem; border-radius: 999px; padding: 6px 10px; background: rgba(138, 90, 54, 0.12); color: #744628; }
.path-panel { display: flex; flex-wrap: wrap; gap: 10px; color: var(--muted); padding: 10px 2px 22px; }
.detail-grid { display: grid; grid-template-columns: minmax(0, 1.28fr) minmax(300px, 0.72fr); gap: 24px; align-items: start; }
.detail-main, .detail-side { display: grid; gap: 18px; }
.info-block { padding: 22px; border-radius: 24px; }
.info-block ul { margin: 0; padding-left: 18px; }
.route-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.route-item, .path-card { padding: 14px 16px; display: flex; flex-direction: column; gap: 8px; }
.deep-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.source-item-deep { padding: 16px; }
.sticky-viewer { position: sticky; top: 92px; }
.plate-full { width: 100%; background: #fffdf8; border: 1px solid var(--line); border-radius: 18px; padding: 10px; }
.viewer-thumbs { display: grid; gap: 10px; margin-top: 14px; }
.viewer-thumb { display: grid; grid-template-columns: 86px 1fr; align-items: center; gap: 12px; width: 100%; border: none; background: transparent; text-align: left; cursor: pointer; padding: 10px; }
.answer-panel { display: none; margin-top: 14px; padding: 14px 16px; border-radius: 18px; background: rgba(138, 90, 54, 0.12); }
.answer-panel.is-open { display: block; }
.toggle-answer { border: none; border-radius: 999px; padding: 10px 16px; background: rgba(38, 24, 20, 0.08); cursor: pointer; }
.plate-path-group + .plate-path-group { margin-top: 18px; }
.mini-plate-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px; }
.nav-strip { margin-top: 22px; display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.glossary-table { overflow: auto; }
table { width: 100%; border-collapse: collapse; }
th, td { padding: 14px 12px; border-bottom: 1px solid var(--line); text-align: left; vertical-align: top; }
@media (max-width: 980px) {
  .hero, .detail-grid, .part-grid, .chapter-grid, .case-grid, .concept-grid, .plate-grid, .route-grid, .deep-grid, .nav-strip { grid-template-columns: 1fr; }
  .shell-bar { flex-direction: column; align-items: flex-start; }
}
@media (max-width: 640px) {
  .page-wrap { padding: 20px 16px 60px; }
  .hero, .section-block, .info-block { padding: 18px; }
  .card-grid, .mini-plate-grid { grid-template-columns: 1fr; }
}